The present invention relates to a method for manufacturing a plugged honeycomb structure. More particularly, the present invention relates to a method for manufacturing a plugged honeycomb structure, the method being capable of manufacturing simply at a low cost a plugged honeycomb structure in which an amount of deposit on the end face is reduced when it is used as a filter or the like.
In recent years, there have been used ceramic plugged honeycomb structures excellent in thermal resistance and corrosion resistance as filters for collecting dust used for an environmental measure such as antipollution and for recovery of products from high temperature gas in various fields such as chemistry, electric power, steel, and industrial waste disposal. For example, such a plugged honeycomb structure is suitably used as a dust-collecting filter used at high temperature in a corrosive gas atmosphere, such as a diesel particulate filter (DPF) for trapping particulate discharged from a diesel engine (see JP-A-2001-300922).
As shown in FIG. 17, a plugged honeycomb structure used as a dust-collecting filter as described above is provided with a cylindrical honeycomb structure 23 having porous partition walls 22 separating and forming a plurality of cells 24 functioning as fluid passages and a plugging member 26 for plugging one opening of each of predetermined cells and the other opening of each of the remaining cells. In the plugged honeycomb structure 21 shown in FIG. 17, the plugging member 26 is plugging alternatively on the inlet side end face B and the outlet side end face C of the cells 24.
In the case of using the plugged honeycomb structure 21 having such a structure as a DPF or the like, once target gas (G1) is introduced from the inlet side end face B into a cell 24, dust and particulate is trapped by the partition walls 22, and the gas permeates through the porous partition walls 22 and flow in the adjacent cell 24 to give treated gas (G2), which is discharged from the outlet side end face C. Therefore, the treated gas (G2) having no dust and particulate which was separated from the target gas (G1) can be obtained.
The plugged honeycomb structure 21 as described above can be manufactured by preparing a cylindrical unfired honeycomb structure having porous partition walls separating and forming a plurality of cells functioning as fluid passages by extrusion forming, filling plugging slurry containing ceramic in one opening of each of predetermined cells of the unfired honeycomb structure obtained or a fired honeycomb structure obtained by firing the unfired honeycomb structure and the other opening of the remaining cells, and firing the honeycomb structure.
However, in the case of manufacturing such a plugged honeycomb structure in a conventional manufacture method, as shown in FIG. 18, a depression 25 toward inside the honeycomb structure 23 from an end face is formed on an end face of the plugging member 26 on an end face side of the plugged honeycomb structure 21. Such a depression 25 is generally called a “shrunk dent”. For example, when the plugged honeycomb structure 21 is used as a filter such as a DPF, deposit (particulate matter) such as soot accumulates on the depression 25, and there arises the problem that the deposit serves as a core, and deposit easily accumulates on the end face of the plugged honeycomb structure 21.
In addition, though a measure (not illustrated) for flattening an end face of the plugging member having a depression by filling plugging slurry again for the plugged honeycomb structure having the depression the an end face of the plugging member, there arise the problems that the complex manufacture processes raise the cost of manufacture, that, since the plugging member is not unitarily formed, the plugging member filled in the depression later is peeled off due to thermal stress, or the like, and that damage is caused at the portion.